This invention relates to surgical apparatus for performing root canal procedures in narrow channels employing laser energy to effect the removal of tissue from, for example, the root canal of a tooth or removal of tumors from narrow arteries (angeoplasty) or narrow ducts.
A common endodontic procedure is the removal of dental pulp and dentin walls from the root canal of a tooth with a diseased nerve preparatory to filling the root canal with a cement and prosthesis which supports a crown. The removal of the pulp and the dentinal walls has traditionally been accomplished by the use of drills to penetrate the crown of the tooth, followed by mechanical extraction of the pulp from the root canal and mechanical enlargement of the canal walls. The process is made complicated by the fact that the entire nerve must be removed from the root canal, but it is important that the endodontist not penetrate the end of the root canal into the underlying living tissue and open up channels for infection. If in the process of removing the pulp and enlarging the canal walls, the tooth structure is perforated, failure may ensue because of an inadequate seal resulting in bacterial growth in the end of the tooth. In addition, the traditional file may break when cleaning the canal preventing proper sealing and an inadequately sealed root canal will result. A great deal of endodontal technique consists in methods for terminating the removal of tissue at the precise point where the root canal exits the tooth.
The use of lasers of sufficient intensity to excise the tissue in surgical procedures is well known. What is required is laser light of sufficient intensity and precise focus to enable the removal of the tissue accompanied by sufficient exit channels for the waste products of the surgical removal. In many instances, the intense heat of the laser releases gases which require exit channels.
U.S. Pat. No. 5,020,995 disclosed a method and apparatus for performing endodontic treatments that involve removing tissue from the walls of a tooth canal by the use of laser radiation. The method and apparatus of that disclosure requires that a succession of pulses having appropriate energy levels, duration and repetition rate be employed. The patent discloses that the optical fiber that carries the laser radiation be given "a suitable length and diameter to be introduced into a canal". Col. 4, line 13. No further disclosure of configuration of the optical fiber is stated.
PCT Publication WO 90/01907 discloses a dental laser assembly for dental surgery employing a pulsed Nd:YAG beam delivered through an optical fiber. In general, the laser emerges from the fiber and is focused by a columnating lens and mirror arrangement to a point displaced from the end of a handpiece in an orientation similar to that of the tip of a dental drill. A second visible HeNe laser beam is emitted coaxial with the first so that the "cutting tip" is rendered visible. The publication also discloses that high energy levels between 100 Mj/pulse and 5 J/pulse are suitable for endodontic procedures such as root canals, apicoectomies and pulpectomies on a tooth. For this purpose a laser tip 212 (FIG. 10) is inserted into the opened pulp chamber and the laser used to eradicate the soft tissue in the pulp chamber. No further description of the configuration of the laser tip is given and the figure shows a pencil point configuration. There is no discussion of modifications of the end of the optic fiber or laser tip to particularly suit it for use in endodontic procedures.
PCT publication WO 89/08432 discloses a laser device for dental applications, particularly for removing enamel and dentin. It suggests the use of a conical or frustro-conical contacting tip to concentrate the laser energy at its apex.
There has been some concern on the part of surgeons who use lasers as scalpels that the laser beam not emerge freely from the end of the scalpel so as to require precise positioning of the scalpel at a distance from the incision. Devices have been suggested which employ fiber optic conduit means for the laser beam and terminate in configurations which cause the laser beam to emerge close to the end of the fiber optic. In this way, the surgeon can control the position of the cut in the same way that he would with a conventional scalpel, namely, by contacting the surface of the tissue to be excised with the tip of the scalpel, which is in this case, the tip of the fiber optic.